UPDATE: DOJ, Ill. Sue Edison International Unit For Clean Air Violations

The federal government and the state of Illinois sued an Edison International (EIX) unit Thursday for alleged Clear Air Act violations at six Illinois power plants.

Federal and state officials allege that Edison unit Midwest Generation made major modifications to six coal-fired power plants without installing required pollution-control equipment.

The lawsuit, filed in federal court in Chicago, alleges the power plants have been illegally emitting "massive amounts" of pollutants.

Regulators are asking the court to order Midwest Generation to install new pollution-control technologies at the plants. They are also seeking civil fines for the alleged violations.

A U.S. Justice Department spokesman declined to comment on the total amount of fines that federal and state regulators are seeking.

The lawsuit potentially could expose the company to tens of millions of dollars in fines and pollution-control costs.

Regulators allege that the Clean Air Act violations have occurred for a decade, and maximum fines for such violations range from $27,500 to $37,500 per day.

Midwest Generation spokesman Douglas McFarlan said the company reached a major agreement with Illinois in 2006 that required it to operate under some of the strongest coal-plant regulations in the country.

Midwest Generation is open to exploring a possible settlement, McFarlan said, but added, "We have a progressive record of environmental performance and leadership that we will be prepared to vigorously present and defend."

He said many of the power-plant modifications at issue in the case took place before Midwest Generation bought the facilities.

With Thursday's lawsuit, the Justice Department has sued three coal-fired power-plant operators this year for Clean Air Act violations. The other two cases involve Westar Energy Inc. (WR) and Louisiana Generating LLC, a unit of NRG Energy Inc. (NRG).

Shares of Edison International traded recently at $33.79, down 28 cents, or 0.8%.

-By Brent Kendall, Dow Jones Newswires; 202-862-9222; [e-mail]